Police, health experts and utility chiefs yesterday urged members of the public not to panic as concerns over water supply and sanitation escalated in the worst-hit flooding areas.

The number of homes facing a fortnight without water is expected to grow and people more than 40 miles away from Gloucester, at the centre of the disaster, have been asked to cut their water usage.

Although Severn Trent insisted there was enough to go round, many people in Gloucestershire complained that bottles of drinking water were not reaching them and bowsers - portable water containers - were running dry. Health chiefs were making contingency plans to deal with infections caused by the shortage of clean water and sewage mixing with river water and inundating homes and streets.

As the waters of the River Severn finally began to recede, Hilary Benn, the environment secretary, told MPs the government would top up the £14m flood recovery fund with a further £10m. He praised the "heroic" efforts of the armed forces in saving a power station from flooding but said the emergency was "not yet over".

A British Red Cross appeal for flood victims raised more than £300,000 in its first hour, with donations from Tesco, Halifax and GlaxoSmithKline, and £100,000 from the charity's disaster fund.

The Queen sent a message of support to victims of the floods and said she was "shocked and deeply concerned" by the extent of the damage.

After Monday night's operation to save Walham station, engineers restored power to 48,000 homes in Gloucester and Tewkesbury as Castle Meads sub-station was repaired. But the chief constable of Gloucestershire, Tim Brain, said the crisis was "effectively a wartime situation".

More than 250 soldiers and sailors are helping the emergency services, some of whom were said to be exhausted after weeks of floods. There are 700 firefighters working round-the-clock in Gloucestershire, where calls have totalled a quarter of the usual 8,000 a year.

Yesterday 140,000 homes in Gloucester, Cheltenham and Tewkesbury were still without tap water after the inundation of the Mythe treatment centre, near Tewkesbury. Supplies were being stretched at two other treatment plants, in the Forest of Dean and at Strensham, north of Bristol, threatening homes further afield.

Alan Payne, senior engineer at Severn Trent, asked people in Worcestershire and Warwickshire not to hoard water and to use as little as possible. "If people panic then there will be a knock-on effect."

Supported by military personnel, engineers were hoping to get into the swamped treatment centre yesterday. But it will be two weeks before it is operational again.

Mr Payne insisted there was water for everyone. Up to 3m bottles of drinking water were available each day and by this morning 900 bowsers were set to be on street corners. Eighty water tankers were keeping them topped up.

Still, in some places they ran out and volunteers began rationing supplies - two 1 litre bottles to households where young children and elderly people lived. Police supervised handing out of bottled water in the car park at Tesco in Quedgeley, Gloucester, as hundreds queued.

Some residents in Cheltenham complained supplies had been slow to reach them and the MP for Tewkesbury, Laurence Robertson, said villages in his constituency were short of clean water.

The director of public health at Gloucestershire Primary Care Trust, Shona Arora, said sanitation was becoming an issue. She urged residents not to put human waste into bins but only to flush when absolutely necessary.

Six severe flood warnings and 28 other flood warnings were still in place yesterday, and people in towns along the Thames valley were warned to expect further flooding. Possible heavy rain later in the week meant some flood warnings were likely to remain in place.

Three of the severe warnings apply to the Severn, at Gloucester, Tewkesbury, and between Tewkesbury and Worcester, and three in Oxfordshire, two on the Thames and one on the River Ock. Blackspots included Pangbourne, Purley and the Reading area, where the river was expected to peak at about 7am.

There were growing calls for the government to seek EU help, as Mr Benn faced more pressure to explain whether it had failed to implement successive reports proposing the Environment Agency take charge of all flooding responsibilities.

Peter Ainsworth, the shadow environment secretary, said at least 25 official reports since 2000 had given warning on Britain's flood preparedness.